This invention relates to vehicle mounted lift devices, and more particularly, to a safety barrier for such a device which prevents accidental falling of a wheelchair from the lift.
Transportation of persons confined to wheelchairs is greatly facilitated by the use of wheelchair lifts mounted on the transporting vehicles. These lifts typically comprise a powered platform which elevates the wheelchair and occupant from ground level to a height sufficient to allow the wheelchair to be maneuvered into the vehicle. This allows a person to board the vehicle while remaining seated in the wheelchair and without the difficulties attendant upon dismounting the person from the wheelchair. Likewise, the lift is also utilized to return the wheelchair and occupant to ground level when disembarking the vehicle.
The safety features of a wheelchair lift are of critical importance because the wheelchair is highly mobile and could inadvertently roll off of the lift platform. The height to which the wheelchair must be elevated to provide entry into a vehicle such as a van or bus mandates that great care be exercised to prevent injuries which would result if the wheelchair would fall from the platform. The platforms are subject to intermittent movements during the lifting and lowering process which could cause the wheelchair to begin rolling. Further, the drive mechanism in powered wheelchairs may also be inadvertently engaged during the loading process and cause the wheelchair to move with considerable force. Such unexpected movements can and sometimes do result in serious injury when the wheelchair falls from the lift platform.
In order to reduce the opportunity for a wheelchair to roll off the loading platform, safety barriers or rails have been provided on the sides and open end of the platform. While many of such barriers have succeeded in minimizing the risk for injury to users of the lifts on which they are installed, a need has developed for even greater security in this respect. Many barriers currently in use are subject to the possibility that they may not always be operative when the lift is in use. Some barriers are not strong enough to positively assure against accident and resultant injury.
The design of more effective safety barriers for lift platforms is now receiving considerable attention. Because of the many safety hazards possible with the use of conventional wheelchair lifts and the effect which such hazards have on the public health and safety, the U.S. Department of Transportation, Urban Mass Transportation Administration, has promulgated safety specifications which are proposed for wheelchair lifts. These specifications require that a lift be provided with an outer barrier which retains a wheelchair on the lift platform under all reasonably anticipated conditions when the platform is above the ground loading position. This requires a barrier which will always be in proper position during the lifting and lowering operations and which is capable of absorbing the tremendous energy from the impact of a loaded wheelchair under maximum power without falling and without permitting the wheelchair to climb over the barrier under such conditions.